Chapter 6 - Cells At Work - Cell Metabolism Flashcards
What is a nutrient
A nutrient is any substance in food that is used for growth, repair or maintaining the body, that is any substance required for metabolism.
What are the six groups of nutrients?
Water Carbohydrates Lipids Proteins Minerals Vitamins
How is water a nutrient
Water is important in metabolism because it is the fluid in which substances are dissolved. Chemical reactions in the cell occur in water, and water molecules actually take in some reactions.
Why is carbohydrates a nutrient?
Carbohydrates are the main source of energy for cells. Complex carbohydrates are broken down to simple sugars, particularly glucose which can then be broken down in cellular respiration
How are lipids a nutrient?
Lipids are an important energy source.
They are broken down into fatty acids and glycerol.
Glycerol can then enter the glycolysis pathway and is broken down to release energy in a similar way to glucose.
What are proteins a nutrient?
Proteins are broken dojo into amino acids. Amino acids can be broken down into new proteins.
With regards to metabolism, the most important proteins made are enzymes.
Enzymes control metabolism by controlling the chemical reactions that occur in the body,
Proteins can also be used as a source if energy but only if the supply of carbohydrates and lipids is inadequate.
Why are minerals considered a nutrient
Minerals are important for metabolism because they may be a part of enzymes, may function as co-factors for enzymes or may be a part of substances like ATP that are involved in metabolism
Why are vitamins a nutrient
Vitamins act as co-enzymes for many of the chemical reactions of metabolism
What is metabolism?
All the chemical reactions that take place in cells, and therefore in the organism of which the cells are a part, is referred to metabolism.
*METABOLISM IS CONCERNED WITH THE MAINTAINING A BALANCE BETWEEN ENERGY RELEASE AND ENERGY UTILISATION
What are the two different types of metabolism and explain them.
Catabolism; reactions in which large molecules are broken down into smaller ones
*reactions release energy
Anabolism; reactions in which small molecules are built up into larger one
*requires energy
What are organic compounds?
Organic compounds have large molecules that always contain the element carbon
Carbohydrates, amino acids, proteins, lipids and nuclei acid
What are inorganic substances
Do not contain carbon in chemical composition or if they do they are really small molecules
CO2, water, oxygen
Carbohydrates breakdown
Carbohydrates always contain; carbon, hydrogen and oxygen. There are always twice as many hydrogen atoms as oxygen
They can be broken down into
- monosaccharides; Simple sugars or single unit sugars Eg. Glucose, fructose and Galactose
- Disaccharide; are two simple sugars joined together Eg. Sucrose, maltose, and lactose.
- polysaccharides; are large numbers of simple sugars joined together Eg. Glycogen, cellulose and starch
Breakdown of protein
Proteins always contain carbon oxygen, hydrogen and NITROGEN. And often Sulfur and phosphorus
They are made up of large numbers of smaller molecules called AMINO ACIDS. About 20 different; glycine, alanine, valine and glutamic acid.
The bond that forms between amino acids is called ‘peptide bond’.
Two amino acid joined together by a peptide is called ‘dipeptide’
10 or more amino acids joined is a ‘polypeptide’
Proteins consists of 100 or more amino acids - each chain is folded in a unique way,
Proteins are important structural materials in the body.
All enzymes are proteins, so proteins are involved in all the chemical reactions of the body.
Break down of lipids
Lipids contain carbon, hydrogen and oxygen, but much less than carbohydrates.
Examples; FATS - stored in the body as energy reserves; PHOSPHOLIPIDS; important in cell membrane
STEROIDS; including cholesterol and sex hormones
Each fat molecule consists of one molecule of glycerol and one, two or three FATTY ACID molecules
The type of fat stored in the body (and 98% of fat in foods) is TRIGLYCERIDES- glycerol plus three fatty acids
Breakdown of nucleic acid
Nucleic acids are very large molecules containing carbon, hydrogen, oxygen, nitrogen and phosphorus.
They are made of nucleotides, each which contains a nitrogen base, a sugar and a phosphate
The two main kinds of nucleic acid are RIBONUCLEIC ACID, RNA
AND DEOXYRIBONUCLEIC ACID, DNA
RNA consists of single chain nucleotides that contains sugar ribose
DNA consist of two chains of nucleotides that contain sugar deoxyribose
What are enzymes?
Enzymes are proteins that allow chemical reactions to take place at normal body temperature.
Without enzymes theses reactions theses reactions would be too slow to be any use to the body.
- enzymes reduce the activation energy needed to begin a reaction.
Eg thus when our cell ‘burn’ glucose in respiration, the reaction an occur at body temp instead of higher temp of combustion
What is activation energy?
The energy needed to get a chemical reaction started is called ACTIVATION ENERGY
- enzymes reduce the activation energy needed to begin a reaction.
Eg thus when our cell ‘burn’ glucose in respiration, the reaction an occur at body temp instead of higher temp of combustion
What is a substrate
The molecules on which an enzyme acts are called SUBSTRATE.
- enzymes are specific. Each enzyme will combine with only one particular substrate and therefore involved in only one specific reaction.
This occurs because the enzyme and the substrate have a shape and a structure that allow them to fit together. Have characteristics that are complementary to each other
Lock and key method - key = enzyme, - lock = substrate
What is the active site
The part of the enzyme molecule that combines with the substrate is called ACTIVE SITE
What is enzyme- substrate complex
When the enzyme and substrate are combined they are called enzyme substrate complex
What are the factors affecting enzyme activity? ( 7 )
- The higher CONCENTRATION of enzyme, the faster the rate of a chemical reaction. By regulating the type and amount of enzymes present, the body is able to control which reactions occur and the rate at which they proceed.
- INCREASE SUBSTRATE CONCENTRATION also increases the rate of the reaction. This occurs because there will be more substrate molecules coming into contact with the enzyme molecules. Beyond a certain concentration, however, increasing the substrate will cease to have an effect because all enzyme molecules will be fully occupied.
- The products of the reaction must be continually removed, otherwise the rate of the reaction will slow because it becomes more difficult for the substrate molecules to make contact with the temperature molecules
- Temperature influences enzyme activity. The rate of most chemical reactions increase as temperature increases. This true for enzymes but only within a limited temperature range. Because enzymes are proteins, beyond 45-50°C their structure Changes and they are inactivated. The temperature at which an enzyme works best is called optimum temperature. Usually between 30-40°C
- Enzymes are very sensitive to the pH of the medium in which a reaction is taking place. Each enzyme has a optimum pH at which it will work most effectively.
- Many enzymes require the presence of certain ions or non-protein molecule before they will catalyse a reaction; Substances such as Co-factors .
Cofactors change the shape of the active site so that the enzyme can combine with the substrate. Without the cofactors the molecule is intact but cannot function. Some cofactors are no protein organic molecules called co-enzymes. Many vitamins functions as co-enzymes - Enzyme inhibitors are substances that slow or even stop the enzyme’s activity. Inhibitors may be used by cells to control reactions so that products are produced in specific amounts. Many drugs are enzyme inhibitors Eg penicillin inhibits an enzyme in bacteria that is involved in construction of the cell wall.
What is cellular respiration?
Cellular respiration is one of the most important thing metabolic processes in any cell. It is the process by which organic molecules, taken in as food, are broken down in the cells to release energy for the cell’s activities- activities such as movement of the cell p, uptake of materials from the surroundings or production and secretion of new chemical compounds.
Draw lock key method
Enzyme + substrate -> enzyme- substrate complex -> enzyme +product
Explain the process of cellular respiration in equation
Glucose + Oxygen —> carbon dioxide + water + energy
C6H6O6 + 6O2 —> 6CO2 + 6H20 + energy
Explain Energy from cellular respiration
In then complete break down of glucose to CO2 and water about 60% of the available energy is released to cells as heat. Cells cannot utilise heat energy, but it is important in keeping body temperature constant as heat is always lost to the environment
The remaining energy from cellular respiration is used to from a compound called ADENOSINE TRIPHOSPHATE OR ATP.
*ATP is formed when an inorganic phosphate group is joined to a molecule of ADENOSINE DIPHOSPHATE (ADP).
The phosphate groups in ATP are joined by high-energy chemical bonds. Some of the energy from cellular respiration is stored in the bond between the ADP molecule and third phosphate group.
This bond is more easily broken than the bond between the first and second phosphate groups
The removal of the third phosphate group releases the energy in the bond, ATP can thus be used to transfer the energy released in cellular respiration to process in the cell that require energy.
The ADP formed when the energy is released can be reused to store some more of the energy from cellular respiration. Thus, ATP acts as a go-between - a way of transferring energy from cellular respiration to cell processes that utilise energy.
Explain the difference between Anaerobic respiration and Aerobic respiration
Anaerobic respiration is a process of cellular respiration that does not require any oxygen present. - occurs in the cytoplasms of the cell
- used in the first 1-2 mins of exercise
- produces less oxygen
Aerobic respiration is a process of cellular respiration which requires oxygen to be present - occurs in mitochondria
- used when heart rate and breathing rate rises
- Produces more oxygen
Explain the process of Anaerobic respiration
- The first phase of glucose breakdown is known as GLYCOLYSIS
* it is broken down in a series of 10 steps INTO TWO PYRUVIC ACIDS - since there is no oxygen present the TWO pyruvic acids provided in glycolysis is converted to LACTIC ACID
- Glycolysis Of one glucose molecule releases enough energy to convert to two molecules of ADP to ATP
- The enzymes required for anaerobic respiration are found in the cytosol of the cell, so this process occurs in the cell cytosol
- It is important during vigorous physical activity when the respiratory and circulatory systems are unable to supply muscle cells with enough oxygen to meet all the energy demands of the contracting muscles. In such circumstances anaerobic respiration produces extra energy.
However the accumulation of lactic acid in the cell can cause muscle pain - Lactic acid from anaerobic respiration is taken by the blood to the liver where it can be recombined with oxygen to from GLUCOSE and eventually GLYCOGEN
* As this process requires oxygen, when Cells are respiring anaerobically the body is incurring OXYGEN DEBT.
AFTER vigorous exercise one continues to breathe heavily for some time because the oxygen debt must be REPAID by converting lactic acid to glucose.
The extra oxygen required after exercise may also be called OXYGEN RECOVERY
Summarise the anaerobic respiration in an equation
1 glucose molecule —> GLYCOLYSIS = 2 ATP molecules and 2 pyruvic acid molecules - - - - > (no oxygen available) —> 2 lactic acid molecules
Occurs in cytosol
Explain the process of aerobic respiration
Aerobic respiration is the breakdown of Glucose to carbon dioxide and water which requires oxygen.
- The two Pyruvic molecules in glycolysis is broken down into carbon dioxide and water in the mitochondria.
* mitochondria is a double membrane organelle, with outer shaping the membrane and the inner is folded inwards for increase surface area of chemical reactions to occur. Enzymes for the reactions of aerobic respiration are attached to the internal membrane so that where the process occurs. - To complete the breakdown of glucose, the two pyruvic acid molecules produced must enter a mitochondrion where enzymes are available to allow two more series of reactions to occur.
- The first reaction is called the Citric or Kreb Cycle which results in the formation of two more ATP molecules from the Pyruvic acid molecules
- The second series of reactions of reactions known as ELECTRON TRANSPORT SYSTEM, can produce up to 34 molecules of ATP from the products of one molecule of glucose.
Thus aerobic respiration of one molecule of glucose has the potential to generate 38 molecules of ATP( 2 from glycolysis, 2from kerbs cycle and up to 34 in electron transport mechanism.
Equation of the number of ATP produced in aerobic respiration
C6H12O6 ——————————————> 6CO2 +6H2O
38 ADP + 38 P —> ATP
Summary of the process of Aerobic respiration in equation
1 - glucose molecule —> 2x ATP + 2x Pyruvic acid molecules ——> (inside mitochondria) kerb cycle and electron transport system (up to 36 ATP molecules + 6CO2 + 6H2O)
Theoretical maximum yield
A yield of 38 ATP molecules from the energy contained in one molecule of glucose is a theoretical maximum. The actual ATP yield is lower than this.
Because the reactions of aerobic respiration takes place in the mitochondria and because The respiration release 95% of energy needed to keep the cell alive, the mitochondria are known as the powerhouses of the cell.
How does the cell use energy from chemical energy of glucose (from food)
Hear
Chemical energy in ATP - building complex molecules - cell division and growth - movement of cell organelles - movement of the whole cell - maintaining cell organisation - Active transport - transmission of nerve impulses —- heat energy —-
What synthesis
Synthesis is the combining of small molecules to make larger molecules - same as anabolism
Eg energy transfer of ATP
In a similar way glycogen molecules can be synthesised by joining glucose units together and glucose can be synthesised from lactic acid and oxygen. Synthesis requires both matter bonds that hold smaller units together.
